UNIVERSITY  OF  CALIFORNIA 

AGRICULTURAL  EXPERIMENT  STATION 
E.  W.   HILGARD,    Director 


PRESERVATION  OF  UNFERMENTED  GRAPE-MUST 


By  F.  T.  Bioletti  and  A.  M.  dal  Piaz 


BULLETIN    130 


BERKELEY 

THE    UNIVERSITY    PRESS 
August,   1900 


PRESERVATION  OF  UNFERMENTED  GRAPE-MUST. 

By  Frederic  T.  Bioletti  and  A.  M.  dal  Piaz. 


The  use  of  unfermented  grape-juice  or  "must"  as  a  beverage,  both 
in  health  and  sickness,  has  been  common  in  vine- growing  countries 
from  time  immemorial.  It  has,  however,  until  lately  been  restricted 
to  the  immediate  vicinity  of  the  vineyards  and  the  season  of  ripe 
grapes.  This  is  owing  to  the  great  facility  with  which  fruit  juices  of 
all  kinds  spoil  within  a  few  days  after  being  expressed  from  the  fruit, 
unless  preserved  artificially.  The  great  progress  made  within  the  last 
few  decades  in  methods,  both  legitimate  and  illegitimate,  of  food 
preservation,  has  made  it  possible  to  keep  grape- juice  for  an  indefinite 
period,  and  to  make  use  of  it  as  a  beverage  at  all  seasons  and  in  all 
places.  Accordingly  the  manufacture  of  grape-must  has  attained 
notable  proportions  in  some  European  countries,  and  in  some  parts  of 
the  United  States.  Its  use,  however,  has  up  to  the  present  day  been 
almost  exclusively  medicinal,  although  it  is  one  of  the  most  wholesome 
and  agreeable  beverages  known,  in  health  as  well  as  disease.  The 
cause  of  this  restricted  use  is  twofold.  In  the  first  place,  in  order  to 
simplify  and  cheapen  the  processes  of  manufacture,  injurious  preserva- 
tive agents  have  been  made  use  of  by  the  unscrupulous,  and,  in  the 
second  place,  the  lack  of  the  necessary  special  knowledge  and  technical 
skill  has  resulted  in  many  failures  of  attempts  to  preserve  the  must 
in  a  legitimate  manner,  so  that  the  price  has  been  necessarily  too  high 
for  the  regular  consumer. 

It  is  to  remedy  this  lack  of  knowledge  on  the  part  of  the  manu- 
facturer, to  warn  the  consumer  against  the  injurious  effects  of  anti- 
septics, and  to  call  attention  to  the  merits  of  this  delicious  beverage, 
that  this  Bulletin  is  written.  More  stress  is  laid  on  general  princi- 
ples than  on  actual  methods,  as  the  methods  will  vary  considerably 
according  to  the  scale  on  which  the  manufacture  is  conducted  and 
according  to  the  facilities  and  appliances  at  the  disposal  of  the  indi- 
vidual manufacturer.  The  business  can  be  conducted  profitably  with 
either  small  or  large  quantities,  but  must  necessarily  be  commenced 
on  a  modest  scale  by  the  inexperienced.  The  directions  given  here 
should  enable  almost  any  grape- grower  to  commence  operations, 
and  gradually,  as  he  acquires  confidence  and  skill,  to  engage  more 
largely  in  what  should  be  an  important  industry  in  California. 


Composition  of  Grape- Must. — A  consideration  of  the  following- 
table,  showing  the  constituents  of  the  normal  juice  of  ripe  grapes,  will 
make  clear  its  value  as  a  nourishing  beverage  in  health,  and  also  its 
therapeutic  efficacy  in  certain  cases  of  disease: 

Parts  in  1,000. 

Grape  sugar  (dextrose  and  levulose)  18U  to  280 

Free  organic  acids  (tartaric,  malic,  tannic)  1  to    10 

Salts  of  organic  acids  (cream  of  tartar,  poo.   sium  malate, 

calcium  tartrate,  calcium  malate 4  to      8 

Ash  (containing  potassium,   sodium,  calcium,  magnesium, 

ferric  oxide,  phosphoric  and  sulfuric  acids).... 3  to      5 

Nitrogenous  matter  (proteids,  amido -compounds) 3  to    10  ■ 

This  table  shows  that  some  of  the  principal  constituents  of  wine, 
such  as  alcohol,  glycerine,  etc.,  are  totally  lacking  in  pure  grape-juice; 
and  it  is  to  be  noted  that  it  contains  no  unwholesome  substance  of 
whatever  kind. 

Grape- juice  should  and  can  be  delivered  to  the  consumer  so  as  to 
contain  no  other  substances  than  those  shown  above.  If  chemical 
analysis  shows  any  other  ingredients,  a  fraud  has  been  practiced;  and 
as  all  the  additions  usually  made  are  in  the  nature  of  antiseptics  or 
preservatives,  they  are  all  more  or  less  injurious.  All  the  antiseptics 
used  are  easily  detected  by  more  or  less  simple  chemical  tests,  and  if 
an  effective  pure-food  law  were  in  operation  it  would  be  easy  for  the 
consumer  and  the  honest  producer  to  protect  themselves  by  occasional 
chemical  analyses  of  the  various  brands  of  grape-must  on  the  market. 
In  the  larger  European  countries,  where  such  laws  do  exist,  the  use 
of  injurious  adulterants  is  rendered  dangerous,  if  not  impossible. 

An  analysis  of  a  pure  grape-must  made  by  a  government  chemist 
in  Austria,  and  one  of  must  put  up  by  Swett  &  Son,  at  Martinez,  made 
by  Mr.  G.  E.  Colby  at  this  station,  gave  the  following  results: 

Analyses  of  Grape -Must. 

Austria.  California. 

Per  Cent.  Per  Cent. 

Solid  contents  by  spindle  (Balling)  21.62  20.60 

Alcohol  .none  none 

Total  acid  (as  tartaric)  .78  .53 

Volatile  acid 01  .03 

Grape  sugar 19.62  19.15 

Cream  of  tartar .61  .59 

Free  tartaric  acid 03  .07 

Ash 37  .19 

Phosphoric  acid .02  .04 

No  cane  sugar,  starch  sugar  or  antiseptics,  were  found  in  the  Cali- 
forniaftor  the  Austrian  musts.  Artificial  (Anilin)  coloring  matter, 
salicylic,  benzoic  and  boracic  acids,  formalin  and  fluorides  were  tested 
for  in  the  California  must  but  none  were  present. 

This  is  approximately  what  should  be  shown  by  any  pure  grape- 
juice.     It  is  instructive  to  compare  this  with  some  partial  analyses, 


made  at  this  station,  of  some  of  the  beverages  offered  to  the  consumer 
in  California  under  such  titles  as  "Unfermented  Wine,"  and  "Pure 
Grape  Juice,"  recommended  for  invalids  and  for  communion  purposes: 

SAMPLE   1-  PerCent. 

Solid  contents  by  spindle 22.00 

Total  acids  (as  tartaric) .59 

Sulfurous  acid  (antiseptic) 06 

SAMPLE   2'  Per  Cent. 

Solid  contents  by  spindle '. 20.80 

'  Alcohol,  by  volume  2.00 

Salicylic  acid  (antiseptic) 3.90 

The  first  sample  was  sold  as  a  "curative  for  throat  and  lung 
troubles."  The  amount  of  sulfurous  acid  it  contained  was  sufficient  to 
cause  throat  and  lung  as  well  as  digestive  troubles  in  a  healthy  person. 
The  second  sample  was  sold  as  "pure  unfermented  grape-juice,"  but 
besides  containing  a  large  amount  of  the  injurious  antiseptic  salicylic 
acid  (more  than  twenty  times  as  much  as  was  necessary  to  preserve  it) , 
it  contained  two  per  cent,  of  alcohol.  Even  healthy  persons,  much 
more  invalids,  would  contract  severe  indigestion  from  the  use  of  such 
a  product,  which  is  a  fraud  upon  the  public. 

Causes  of  spoiling. — In  order   to    make    clear  the  nature  of  the 
problem  which  must  be  solved  in  order  to  preserve  grape-juice  indefi- 
C\r\  r\  ***£&  nitely,  a  short  account 

O       ^r£==^3**k  °*'  ^ne  causes  °f  spoiling 

^\   0c  $  will  be  useful .    When 

Z3/cW^'&  /I  grapes'  or  any  fruits' 

q?  W&c  J  J    are  gathered,  the  sur- 

//      faces   in    contact   with 

„  o^v.      </\f  *       JJ  the  air  have  the  spores 

rP    *°      /i  of  various  fungi,  yeasts, 

and  bacteria   adhering 

to  them.     All    these 

a,  a',  a".    Various  forms  of  a  mold,  (Mucor). 

c,  d,  e.    Various  forms  of  yeasts,  molds,  and  bacteria.  Spores  are  miCrOSCOpic, 

Fig.   1.-MICRO-ORGANISMS   ON    GRAPES.  but     ^     ^^     Qf      theh, 

appearance,  when  sufficiently  enlarged  by  the  microscope  to  be  visible, 
may  be  obtained  by  reference  to  Fig.  1,  which  shows  various  forms 
of  these  organisms  developed  on  the  skin  of  a  muscat  grape. 

When  the  grapes  are  crushed  and  the  juice  expressed,  the  latter 
will  be  contaminated  by  these  spores,  washed  off  the  skin.  In  the  air 
they  are  dry,  and  therefore  inert;  but  very  soon  after  they  are 
surrounded  by  the  must,  which  is  a  very  favorable  medium  for  their 
growth,  they  assume  an  active  form  and  commence  to  multiply.  If 
the  must  is  warm,  this  change  to  an  active  state  occurs  very  soon  and 


the  consequent  increase  in  numbers  is  proportionately  rapid.  If,  on 
the  contrary,  the  grapes  and  therefore  the  must  be  cool,  the  increase 
is  much  slower;  but,  eventually,  if  left  alone  the  organisms  increase 
until  the  must  ferments.  This  fermentation  consists  principally  in 
the  changing  of  the  grape  sugar  into  alcohol  and  carbonic  acid,  and 
is  the  essential  part  of  the  process  which  changes  grape- juice  into  wine. 

The  main  object,  then,  of  the  producer  who  wishes  to  place  "pure 
unfermented  grape-juice"  upon  the  market,  is  to  permanently  prevent 
this  fermentation.  Besides  this,  the  grape-juice  must  be  quite  clear, 
in  order  to  present  an  attractive  appearance  to  the  consumer. 

To  attain  the  first  object  there  are  two  general  groups  of  methods, 
which  may  be  called  respectively  chemical  and  physical .  All  the 
chemical  methods  consist  in  the  addition  of  germ  poisons  or  antisep- 
tics, which  either  kill  the  microscopic  organisms  of  fermentation  or 
permanently  prevent  their  growth  and  increase.  Of  these  substances 
the  principal  used  are,  besides  salicylic  and  sulfurous  acid  already 
mentioned,  boracic  acid,  saccharin,  and,  of  late,  formalin.  Many 
patent  preservatives  are  found  on  the  market,  but  they  nearly  all 
contain  one  or  more  of  these  substances  as  their  active  principle. 
They  are  all  injurious  to  digestion  and  in  other  ways;  and  it  may  be 
said  in  general  that  any  substance  which  prevents  fermentation  will 
also  interfere  with  digestion,  and  is  therefore  to  be  avoided. 

The  Physical  methods  work  in  one  of  two  ways:  they  remove  the 
germs  by  some  mechanical  means,  such  as  a  filter,  or  a  centrifugal 
apparatus;  or  they  destroy  them  by  heat,  cold,  electricity,  etc.  The 
methods  which  depend  upon  the  removal  of  the  germs  are  inapplicable, 
as  this  cannot  be  done  thoroughly  except  with  very  small  quantities 
of  liquid,  and  the  minute  organisms  with  which  we  have  to  deal  will 
soon  increase  sufficiently  to  spoil  the  liquid,  if  a  single  one  escapes  the 
filter.  One  yeast-cell,  for  instance,  at  ordinary  temperatures  will 
increase  to  tens  of  millions  in  three  or  four  days ;  and  if  the  tempera- 
ture is  warm  the  increase  will  be  still  more  rapid.  We  are,  then, 
reduced  to  those  physical  methods  which  destroy  the  germs;  and  of 
these  the  only  one  which  has  been  found  useful  in  this  connection  is 
the  use  of  high  temperatures.  This  method  depends  on  the  fact  that 
when  a  liquid  is  heated  up  to  a  sufficiently  high  temperature  all 
organisms  present  are  killed.  This  temperature  is  called  the  "death 
point,"  and  differs  for  each  particular  variety  of  organisms.  The 
death  point  will  also  differ  according  to  the  composition  of  the  liquid 
in  which  the  organism  is  immersed.  Yeast,  for  instance,  is  killed  at 
a  lower  temperature  in  must  than  in  water,  on  account  of  the  acidity 
of  the  former.  Time,  also,  is  a  factor  in  determining  the  death  point. 
An  organism  may  not  be  killed  if  heated  to  a  certain  degree  quickly 


and  as  quickly  cooled ;  while  if  it  is  kept  at  that  same  degree  for  some 
time  it  will  be  killed.  Some  tests  made  at  this  station  with  a  pure* 
yeast  isolated  from  a  California  wine  illustrate  these  facts.  The 
yeast  was  placed  in  must  which  had  previously  been  completely  freed 
from  all  germs,  and  wTas  heated  to  various  temperatures  for  various 
lengths  of  time,  with  results  as  follows:  The  initial  temperature  of 
the  must  was  20°  C.  (68°F.)  and  the  yeast  was  killed  by  heating 
it  gradually  up  to  60°  C.  (140°  F.)  in  fifteen  minutes;  that  is  to  say, 
the  time  taken  to  bring  the  temperature  from  20°  C.  (68°F.)  to  60°  C. 
(140°  F.)  was  fifteen  minutes,  and  at  the  end  of  this  time  the  must 
containing  the  yeast  was  allowed  to  cool  in  a  room  at  20°  (68°  F.). 
This  same  yeast  was  not  killed  when  heated  in  twenty-five  minutes 
from  20°  C.  (68°  F. )  to  50°  C.  ( 122°  F. ) ,  nor  even  when  kept  at  the  latter 
temperature  for  five  minutes  longer.  But  when  kept  at  this  tempera- 
ture for  ten  minutes  longer,  all  the  yeast  cells  were  killed.  Another 
test  with  the  same  yeast  showed  that  if  heated  from  20°  C.  (68°  F.)  to 
45°  C.  (113°  F.  )in  twenty  minutes,  and  then  kept  at  the  latter  tempera- 
ture for  twenty  minutes,  few  or  none  of  the  yeast  cells  were  killed, 
though  in  thirty  minutes  most  of  them  were  rendered  incapable  of 
growth.  However,  even  in  the  last  case  some  were  left  alive  and 
ultimately  spoiled  the  must.  We  learn  from  these  tests  that  heating 
to  45°  C.  (113°  F.),  even  for  a  somewhat  prolonged  time,  cannot  be 
depended  on  to  sterilize  grape-must,  and  that  even  50°  C.  (122°  F.) 
requires  too  much  time  to  be  practical.  A  heating  to  60°  C.  ( 140°  F. ) , 
however,  would  probably  be  quite  safe,  provided  that  only  this 
particular  variety  of  yeast  were  present  in  the  must.  In  practice, 
however,  we  have  an  unknown  number  of  kinds  of  micro-organisms 
present,  and  some  of  them  may  be  able  to  withstand  a  somewhat 
higher  temperature  than  this. 

It  must  be  kept  in  mind  also  that  fungi,  including  yeasts,  exist  in 
two  states,  the  vegetative  or  growing  state,  and  the  spore  or  resting 
state.  The  latter  is  more  resistant  than  the  former;  and  it  has  been 
found  that  yeast  spores,  for  instance,  to  be  killed  must  be  heated 
about  5°  C.  (9°  F.)  higher  than  the  same  yeast  in  the  growing  state. 
The  above  tests  were  made  with  yeast  containing  no  spores;  but,  as 
in  practice,  spores  may  be  and  undoubtedly  usually  are  present,  a 
temperature  5°  C.(9°  F.)  higher  than  indicated  would  be  necessary. 
Practical  experiments  made  at  this  station  indicate  that  must  can  be 
safely  sterilized  at  a  temperature  of  75°  C.(167°F.)  or  80°  C.(176°F.) 
if  all  the  precautions  indicated  below  are  observed.  At  this  tempera- 
ture the  flavor  of  the  grape-juice  is  hardly  changed,  though  at  between 
90°  C  (194°  F.)  and  100°  C.  (212°  F.)  it  is  slightly  affected. 

*  Pure  in  this  case  means  a  yeast  consisting  of  only  one  variety  of  micro-organism. 


Another  property  of  fungi  and  their  spores,  which  is  of  importance 
in  this  connection,  is  their  great  resistance  to  heat  when  dry.  Yeast 
can  be  heated  in  a  dry  state  to  a  temperature  above  that  of  boiling 
water  without  being  killed;  the  spores  of  some  fungi  (e.g.,  common 
mold)  are  even  more  resistant.  The  bearing  of  this  upon  the  preser- 
vation of  must  is  that  during  the  final  sterilization,  which  takes  place 
in  glass  bottles  or  similar  vessels,  portions  of  the  inner  surface  of  the 
cork  and  of  the  bottle  above  the  liquid  are  comparatively  dry;  and  if 
any  spores  should  be  adhering  to  these  parts  there  is  danger  that  they 
will  not  be  killed,  and  that  afterwards,  when  they  come  in  contact 
with  the  must,  they  will  grow  and  cause  fermentation  or  mold.  For 
this  reason  both  the  bottles  and  the  cork  must  be  thoroughly  sterilized 
before  being  used.  This  can  be  accomplished  for  the  bottles  by  boiling 
them  for  at  least  half  an  hour  after  thorough  washing,  and  then 
allowing  them  to  drain  in  a  place  where  they  are  exposed  to  no 
draughts  or  dust.  This  boiling  should  be  done  as  short  a  time  as 
possible  before  filling  the  bottles,  and  they  should  be  handled  care- 
fully, taking  care  not  to  touch  their  mouths,  for  with  the  greatest  care 
the  hands  cannot  be  kept  free  from  mold  spores.  To  sterilize  the 
corks  this  method  is  not  always  sufficient,  as  spores  that  may  be  in 
cracks  are  liable  to  escape.  For  sterilizing  the  corks,  some  closed 
receptacle  should  be  used  which  will  safely  withstand  considerable 
pressure.  The  corks  when  placed  in  this  receptacle  can  best  be  steri- 
lized by  steam  under  pressure,  which  is  allowed  to  flow  in  until  the 
pressure,  as  shown  by  a  gauge,  is  at  least  ten  pounds.  This  pressure 
indicates  a  temperature  of  about  115°  C.  (239°  F.),  and  should 
continue  for  at  least  twenty  minutes. 

Apparatus  required. — The  apparatus  necessary  for  preserving  grape- 
must  on  any  but  the  very  smallest  scale  consists  of:  1,  a  continuous 
pasteurizer;  2,  a  pressure  filter;  3,  a  pressure  sterilizer  for  corks 
(this  may  be  dispensed  with) ;  4,  a  bottle  pasteurizer;  5,  a  boiler  for 
pressure  steam.  Certain  other  utensils  are,  of  course,  necessary,  but 
they  are  such  as  are  found  in  almost  every  wine-cellar. 

The  manner  of  operating. — The  method  of  proceeding  is  as  follows: 
Sound,  clean  grapes,  preferably  those  having  high  natural  acidity,  are 
picked  carefully,  while  cool,  into  clean  boxes.  They  should  not  be 
too  ripe  or  the  must  will  be  too  sweet  and  difficult  to  clear.  They 
should  be  crushed  as  soon  as  possible  after  picking,  and  the  juice  run 
into  perfectly  clean  puncheons  or  other  receptacles  which  have  been 
previously  steamed.  If  the  must  is  cold — 15°  C.  (59°  F.)  or  under — 
it  may  be  safely  left  to  settle  for  twenty-four  hours  or  more.  This 
settling  is  an  advantage,  as  it  rids  the  juice  of  most  of  the  floating 
solid   matter,  and  facilitates  the   subsequent   filtering.     During  this 


settling  the  must  should  be  closely  watched,  in  order  to  anticipate 
even  a  commencement  of  fermentation.  After  this  settling,  when  the 
must  has  become  almost  clear,  it  is  run  through  a  continuous  pasteur- 
izer, of  one  form  of  which  Fig.  2  gives  an  idea. 

It  is  heated  in  this  to  80°  C.  (175°  F.)  and  should  come  out  cool, 
not  warmer  than  25°  C.  (77°  F.)  and  should  pass  into  fresh  settling 
receptacles.  For  this  purpose  puncheons  or  other  casks  may  be  used, 
if  they  have  been  thoroughly  sterilized  by  steam,  though  the  best 
receptacles  would  doubtless  be  casks  or  vats  of  metal  lined  with 
enamel,  such  as  are  now  made.  The  greatest  care  must  be  taken  to 
avoid  contamination  of  the  must  as  it  flows  from  the  pasteurizer.     It 


ST,  Steam  pipe.      H,  Outlet  for  hot  pasteurized  must.         U,  Inlet  for  unpasteurized  must. 
W,  Water  bath.       P,  Outlet  for  cooled  pasteurized  nmst.     T,  T' ,  Thermometers. 

Fig.  2. — Continuous  Pasteurizer. 
should  pass  directly,  by  means  of  a  block-tin  pipe,  from  the  pasteurizer 
into  the  receiving  casks.  The  end  of  this  pipe  should  be  thoroughly 
sterilized  by  plunging  into  boiling  water,  and  should  never  be  allowed 
to  touch  the  hands  or  any  exposed  surface.  When  a  receiving  cask  is 
full  it  should  be  closed  immediately  with  a  wooden  bung,  sterilized 
preferably  in  the  way  already  described  for  corks.  If  all  these  opera- 
tions have  been  conducted  with  the  requisite  care,  and  the  casks  kept 
in  a  cool  cellar,  the  must  will  remain  without  fermenting  for  many  days 
or  even  weeks.  During  this  time  it  deposits  more  or  less  sediment 
which  has  been  formed  in  heating.     It  is  then  ready  for  filtering. 

Filtration. — This  filtration  is  best  accomplished  by  means  of  a 
filter  so  constructed  that  the  must  passes  upward  through  the  filtering 
medium,  under  pressure.  Such  a  filter,  made  by  the  International 
Filter  Co.  of  Chicago,  is  shown  in  Fig.  3. 


9 


This  filter  consists  essentially  of  two  shallow  bowls  clamped  together  mouth  to 
mouth  with  the  filtering  medium  between  them.  The  unfiltered  must  enters  the 
lower  bowl  through  the  pipe  on  the  right  of  the  figure,  passes  through  the  filtering, 
medium  into  the  upper  bowl  and  makes  its  exit  when  clear  through  the  faucet  a  little 
to  the  left  of  the  middle  of  the  figure.  The  small  faucet  at  the  bottom  of  the  lower 
bowl  is  for  the  purpose  of  cleaning  the  filter.  Occasionally,  when  filtration 
becomes  slow,  this  faucet  is  opened  for  a  few  moments.  This  allows  the  sediment 
accumulated  at  the  bottom  to  escape  and  at  the  same  time  the  entering  must  takes 
a  rotary  course  in  the  lower  bowl,  thus  cleaning  off  the  surface  of  the  filtering 
medium;  so  that  when  the  cleaning  faucet  is  closed  filtration  proceeds  as  before. 
On  a  large  scale,  a  filter  press,  such  as  is  used  in  large  wineries  and  in  beet  sugar 
factories,  might  conveniently  be  used. 

It  is  impossible  to  prevent  a  certain  amount  of  contamination  by 

fungous  spores  during 
nitration;  but  it  should 
be  minimized  as  much  as 
possible  by  the  greatest 
cleanliness,  and  attention 
to  sterilizing  everything 
with  which  the  must 
comes  in  contact.  In 
this  regard  it  should 
be  kept  constantly  in 
mind  that  in  an  ordinary 
room  or  cellar,  where 
there  is  little  dust,  there 
is  comparatively  little 
danger  of  contamination 
from  the  air,  the  main 
danger  being  from  the 
solid  surfaces  with  which 
the  must  comes  in  con- 
tact. The  must  may  be 
bottled  directly  as  it 
flows  from  the  filter,  or 
it  may  pass  into  a  steri- 
lized temporary  recep- 
tacle, from  which  it  is 
bottled.  It  should,  how- 
ever be  placed  in  its  final 
receptacles  (bottles,  etc.) 
the  same  day  on  which 
it  is  filtered,  corked  im- 
mediately, and  sterilized  as  soon  as  possible,  preferably  within  24  hours. 


Fig.  3.— Filter  for  Clarifying  Must. 


10 

Final  sterilization. — On  account  of  the  recontamination  during 
nitration,  a  final  sterilization  must  be  made  after  the  bottles  are  corked. 
This  is  accomplished  by  means  of  a  bottle-sterilizer,  which  the  pro- 
ducer can  construct  himself.  A  simple  and  efficient  form  is  shown 
in  Fig.  4. 

It  consists  of  a  wooden  box  or  trough  provided  with  a  wooden 
grating  placed  about  two  inches  from  the  bottom.  The  bottles,  after 
being  filled  with  the  filtered  must  and  corked,  are  placed  in  perforated, 
or  wire  baskets,  which  rest  upon  the  grating.  The  trough  should 
contain  enough  water  to  completely  submerge  the  bottles.  The  water 
should  be  kept  at  a  constant  temperature  of  about  85°C.  (185°F.)  by 
means  of  a  steam  coil  placed  beneath  the  grating.  The  bottles  should 
be  left  in  this  pasteurizer  for  exactly  fifteen  minutes  if  they  are  one- 
quart  champagne  bottles.  For  other  sizes  it  is  necessary  to  make  a 
test  with  a  bottle  of  must  in  which  a  thermometer  has  been  placed,  in 
order  to  determine  how  long  it  takes  for  the  entire  contents  of  the 
bottle  to  reach  the  required  temperature.  It  has  been  found  at  this 
station,  that  although  the  must  in  the  upper  part  of  a  quart  cham- 
pagne bottle  reaches  75°C.  (167°F. )  in  eight  minutes,  when  surrounded 


DB,  Double  bottom.      ST,  Steam  pipe.      W,  Water  bath.      T,  Thermometer. 
(Bottle,  shows  method  of  adjusting  a  cork  holder  of  sheet  metal.) 

Fig.  4.— Cork  Clamp  and  Pasteurizer  for  Must  in  Bottles. 


by  water  at  85°C.(185°F.)it  requires  fifteen  minutes  before  the  must 
at  the  bottom  of  the  bottle  acquires  that  temperature.  The  sterilization 
in  bottle  should  be  conducted  at  a  temperature  at  least  5°C.  (9°F.) 
lower  than  that  reached  in  the  continuous  pasteurizer.  Thus,  if  the 
water  in  the  first  case  was  kept  at  90°C.(194°F.)  or  95°C.(203°F.)  and 
the  must  attained  a  temperature  of  80°C,  the  water  in  the  bottle 
pasteurizer  should  be  kept  constantly  at  85°C.  and  the  time  of 
pasteurizing  so  chosen  that  the  must  in  the  bottles  will  attain  a 
maximum    temperature  of   75°C.(167°F.)       If  the  final    heating   is 


11 

higher  than  the  first,  it  may  cause  a  precipitation  of  solid  matters  which 
will  make  the  must  cloudy  in  the  bottles. 

During  this  sterilization  in  bottle  the  corks  are  liable  to  be  expelled 
by  the  pressure  developed.  To  prevent  this  they  may  be  tied  down 
with  strong  twine;  but  it  is  a  great  saving  of  time  and  labor  to  use 
some  such  contrivance  as  that  illustrated  in  Fig.  4. 

By  this  operation  the  must  is  thoroughly  sterilized  and  will  then 
keep  unchanged  for  years,  or  until  the  bottles  are  ODened.  If,  however, 
the  bottles  are  to  be  capsuled,  or  kept  in  a  very  damp  place,  there  is 
one  other  cause  of  spoiling  that  must  be  guarded  against.  However 
carefully  all  the  various  operations  are  conducted,  there  are  sure  to  be 
mold  spores  on  the  upper  surface  of  the  cork.  If  this  surface  remains 
dry  these  spores  will  not  grow,  and  are  harmless.  But  when  the  cork 
is  covered  with  a  capsule  the  space  between  the  capsule  and  the 
surface  of  the  cork  finally  becomes  moist,  and  any  spores  there  will 
develop.  Some  molds  have  great  penetrating  power  and  may  force 
their  way  either  through  the  cork,  or  between  the  cork  and  the  neck 
of  the  bottle  (especially  if  the  very  best  quality  of  corks  has  not  been 
used)  and  finally  reach  the  must.  The  molds  which  enter  in  this  way 
do  not,  as  a  rule,  grow  into  the  liquid,  on  account  of  the  small  amount 
of  air  present;  but  they  make  a  moldy  layer  on  top,  which  lessens  the 
selling  value  of  the  must,  if  it  does  not  actually  spoil  it.  This  danger- 
can  be  avoided  by  dipping  the  top  of  the  neck  of  the  bottle  into  a  two 
per  cent,  solution  of  bluestone  and  water,  in  such  a  way  as  to  wet  the 
upper  surface  of  the  cork,  before  putting  on  the  capsule.  The  same 
object  may  be  attained  by  dipping  the  neck,  in  the  same  way,  into 
very  hot,  melted  paraffine.  The  bluestone  acts  by  killing  any  spores 
that  maybe  on  the  cork  or  which  may  find  their  way  there  later.  The 
heated  paraffine  kills  the  spores  present,  and  prevents  later  infection 
by  completely  covering  the  cork  and  keeping  it  dry. 

The  quality  and  character  of  the  grape- juice  prepared  in  this  way 
will  vary  greatly  according  to  the  variety  of  grape  used ;  and  a  pleasing 
variety  may  be  obtained  by  using,  partially  or  wholly,  grapes  of 
high  aroma,  such  as  Muscat,  Isabella,  etc.  The  color  will,  however, 
always  be  white  or  yellowish  except  with  a  few  grapes,  such  as  the 
Bouschets,  which  have  pink  or  red  juice.  Red  must,  however,  can 
be  obtained  by  a  modification  of  the  process  described.  If  the  must, 
after  it  passes  through  the  continuous  pasteurizer,  is  allowed  to  come 
out  hot  and  flow  into  a  vat  containing  the  skins  of  red  grapes,  almost 
any  desired  depth  of  color  ma}^  be  obtained,  depending  on  the  variety 
of  grape  used  and  the  time  during  which  the  hot  must  is  left  in 
contact  with  the  skins.  Must  prepared  in  this  way,  however,  differs 
in  other  respects  than  in  color  from  the  white  must.     Besides  coloring 


.      12 

matter  various  substances  are  extracted  from  the  skins,  the  principal 
being  tannin.  This  makes  the  composition  of  the  red  must  more  like 
that  of  red  wine,  though  of  course  it  still  contains  no  alcohol.  A 
grape-juice  of  this  character  might  appropriately  be  called  "Unfer- 
mented  Wine,"  and  would  doubtless  be  useful  in  medicine,  as  it  would 
possess  certain  tonic  properties  not  found  in  the  white  must.  The 
regular  consumer,  however,  would  in  all  probability  generally  prefer 
the  white  must. 

Grape-must,  containing  as  it  does  generally  from  twenty  to 
twenty-four  per  cent,  of  sugar,  is  too  sweet  for  many  palates  and 
constitutions,  but  it  may  be  diluted  with  water  by  the  consumer  to 
any  desired  extent;  and  a  mixture  of  equal  parts  of  grape-must  and 
carbonated  or  mineral  water  makes  a  beverage  much  appreciated  by 
many  people.  In  Europe  a  certain  amount  of  sparkling  grape- juice 
is  put  up,  i.e.  grape- juice  which  has  been  carbonated,  or  charged 
with  carbonic  acid  gas.  This,  though  an  addition  to  the  natural  juice 
of  the  grape,  cannot  be  looked  upon  in  any  sense  as  a  fraud  or 
adulteration,  and  makes  the  beverage  more  palatable  to  many;  besides 
if  properly  done  it  has  no  injurious  effects  on  the  health  of  the 
consumer. 

In  conclusion  the  following  brief  summary  of  the  main  precautions 
to  be  observed  in  the  manufacture  of  unfermented  grape-must  may  be 
useful : 

1.  Only  clean  and  perfectly  sound  grapes  should  be  used. 

2.  The  grapes  should  be  picked  and  handled  when  cool. 

3.  The  greatest  cleanliness  is  necessary  in  every  stage  of  the  process. 

4.  All  utensils  and  apparatus  used  should  be  cleaned  and  sterilized 
immediately  before  using,  and  as  short  a  time  as  possible  after  using. 

5.  The  last  sterilization  should  be  at  a  temperature  at  least  »5°C. 
(9°F.)  lower  than  the  temperature  used  in  the  first  sterilization. 

6.  Reliable  thermometers  should  be  used,  and  the  temperature 
watched  very  carefully. 


